Three longitudinal studies are proposed to elucidate the mechanisms underlying longterm response to natural and human-caused trauma and the physiological correlates of stress following disasters and motor vehicle accidents. The first will follow participants in the currently funded study of disasters for an additional four years, extending prior analysis of chronic stress in the face of disaster and systematically testing for symptoms of post-traumatic stress disorder and other health problems, physical health difficulties, and psychophysiological evidence of stress. The second study will follow a newly recruited group of disaster victims for three years, beginning one month after the disaster, and will also measure psychological and physiological aspects of stress, symptoms of posttraumatic stress disorder and other psychiatric syndromes, and overall health. By initiating investigation soon after the disaster, this study will extend prior analyses by allowing examination of relationships between acute distress and early responses/symptoms and chronic stress and long-term outcomes. Comparisons between natural and human-caused disasters will be made as a part of both of these studies. The third study will investigate the short and long-term psychophysiological sequelae of another source of trauma, motor vehicle accidents. A group of people involved in motor vehicle accidents will be studied, beginning one month after the accident, for three years and measures will address acute and chronic stress, mental and physical health, and longterm well-being. Comparisons between types of disasters and trauma produced by motor vehicle accidents will address one goal of the project, the evaluation of the generalizability of findings from studies of different sources of trauma. Other objectives of the proposed research include evaluation of physiological changes that precede, accompany, or follow emergence of symptoms of emotional distress, post-traumatic stress, and other mental and physical health problems, and the comparability of patterns of adjustment following different types of extreme stressors.